The present application relates to an optical relay system which relays an optical signal by wavelength division multiplexing.
An optical add/drop multiplexer (OADM) which adds/drops a partial wavelength of a plurality of wavelengths that are multiplexed is introduced into a node device within an optical network which uses wavelength division multiplexing (WDM). Further, in recent years, introduction of a wavelength selective switch (WSS) is underway as a device capable of switching a path of an optical signal having an arbitrary wavelength. By building a network using the wavelength selective switch, it is possible to easily change the path of the optical signal even in the network configured only by the optical signal.
However, compared with a network which relays an optical signal by converting the optical signal into an electrical signal, the optical network which relays the optical signal as it is raises a problem that deterioration of the optical signal accumulates. Therefore, in a case of performing a long-distance transmission of the optical signal, it is necessary to perform signal regeneration by using a relay device to temporarily convert the optical signal into the electrical signal. Japanese Patent Application Laid-open No. 2009-147913 (hereinafter, referred to as “Patent Document 1”) discloses a wavelength selective switch incorporating a regenerative repeater which performs signal regeneration by converting an optical signal into an electrical signal.